Question: $ { \left[\begin{array}{rr}{1} & {-1} \\ {-2} & {2}\end{array}\right]+\left[\begin{array}{rr}{3} & {1} \\ {-2} & {-1}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rr}{1}+{3} & {-1}+{1} \\ {-2}+{-2} & {2}+{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{4} & {0} \\ {-4} & {1}\end{array}\right]}$